how can I get current real-time buffer size in vlc streaming buffer through python-vlc?

[maozezhong]

I want to get the current real-time buffer size while vlc streaming video, How can I get it through python-vlc. real-time buffer size means like, a video is stream from one server to one client, vlc get it and stored it in a buffer pool, and vlc decode the data in the pool so as to show the video currently, what I want is the size or time of video data in the pool during the streaming.

[mrJean1]

The MediaStats class provides some details like the number of bytes read, frames decoded, the bitrate and other things, but there's no buffer size. To get the MediaStats from Python, use

p = vlc.player()
p.set_mrl(<video_file_name>)
p.play()
...
s = vlc.MediaStats()
m = p.get_media()
if m.get_stats(s):
    print(s)
...

Following is an example of the output (with Python 2.7.15) playing one video, but paused:

MediaStats
 read_bytes: 7901716
 input_bitrate: 2.51318240166*
 demux_read_bytes: 7843817
 demux_bitrate: 2.56340408325*
 demux_corrupted: 0
 demux_discontinuity: 2
 decoded_video: 192
 decoded_audio: 291
 displayed_pictures: 65
 lost_pictures: 0
 played_abuffers: 145
 lost_abuffers: 0
 sent_packets: 0
 sent_bytes: 0
 send_bitrate: 0.0

*) Bitrates are conventionally in Ko/s, for kilo-octets-per-sec.

Screen shots of 2 of the Media Information... window panes of the VLC App (on macOS) playing an other video.

[mrJean1]

The latest version 18.7.27 of examples/cocoavlc.py now also shows how to get and interpret MediaStats.

[maozezhong]

@mrJean1 , hello, thank you for your reply. Is it possible to get buffer size through input-bitrate and demux_bitrate ? Like in my opinion, input bitrate means the vidieo data stream to the current pool, and demux bitrate is the data get out from the current pool , So I can simply get buffer size through this two parameter, am I right?

[mrJean1]

Possibly, using one of these cache sizes. But you may have to get that cache size from the VLC App, since there doesn't seem to be a way to get or set any of these from Python.

Here's a screen shot of the VLC 3.0.3 App Preferences -> Input/Codecs -> Advanced caching settings on macOS.

[mrJean1]

It turns out there are command line options to set the caching values:

% /Applications/VLC.app/.../VLC --help --advanced
...
  Subpictures
    Advanced:
      --file-caching <integer [0 .. 60000]>    File caching (ms)
      --live-caching <integer [0 .. 60000]>    Live capture caching (ms)
      --disc-caching <integer [0 .. 60000]>    Disc caching (ms)
      --network-caching <integer [0 .. 60000]>    Network caching (ms)
 ...

From Python, you could set these as follows, untested however:

i = vlc.Instance(["--file-caching=2000 --network-caching=3000"])
p = i.media_player_new()
...

[maozezhong]

@mrJean1 Thanks a lot! It seems to set the caching values means to set the total size of the buffer pool, like, when I set the file-caching=2000, it means the upper limit of buffer pools is 2000ms, in another word, the max time of video the buffer pool can store is 2000ms. what I want to get is the real-time buffer size when streaming the video data, because the pool is not always full, so 2000ms may not be the value I want, am I right? So, any other adivce? correct me if I am wrong~

[mrJean1]

That question is now beyond the Python-VLC project. Ask that again, but at the VideoLan.org support/help page.

[maozezhong]

OK, Thanks a lot anyway!

[mrJean1]

Just to explain, the buffer size is probably not just the bitrate times the caching time.

[maozezhong]

Ok, So (read_bytes -demux_read_bytes ) / input_bitrate may not be the caching time? what is the buffer size exactly?

[mrJean1]

Like my previous comment, this may not be that simple either. Just don’t know and don’t have an authoritative answer, sorry.

[maozezhong]

ok, thank you for your patient reply~

[mrJean1]

As an experiment, the latest examples/cocoavlc.py computes input-caching as (read_bytes - demux_read_bytes) / (input_bitrate * 1000) in seconds and (read_bytes - demux_read_bytes) in bytes.

Typical initial values are around 30 s and 70 KiB for sample videos at about 2 secs, see cocoavlc-snapshotX-TableWindow.pdf. Both those values increase for any time later in the videos.

[floris-vos]

this is closed - I suppose it means that this is just impossible?
I tried with MediaStats, but couldn't get any kind of reasonable buffer or cache info.

[mrJean1]

The MediaStats struct hasn't changed in VLC since the examples shown above. And that's all vlc.py can provide.